Fatigue-proof plate heat exchanger

ABSTRACT

Plate heat exchanger for indirect heat exchange between at least two liquid and/or gaseous media with an essentially parallelepiped-shaped base ( 8 ), means for feeding and removing the media (headers  6, 6   a,    7 ), and a number of passages ( 14 ), arranged essentially like stacks, for indirect heat exchange between media that respectively flow into adjacent passages ( 14 ), whereby the passages are formed by partitions ( 1, 22 ) that are spaced some distance apart, whereby the partitions are spaced some distance apart by end strips ( 4 a,  4 b), the passages have a corrugated profile (fins,  2 ), which is in heat-conductive contact with the partitions ( 1, 22 ) at its wave peaks and wave troughs, and the stack is closed off by a cover plate ( 5, 21 ), characterized in that the ratio between the width of the partition (B) and the repetition interval of the same characteristic of the corrugated profile as, for example, the repetition interval of two wave peaks (wavelength, LP) has a value in the range of between 15 and 80.

The invention relates to a plate heat exchanger for indirect heat exchange between at least two liquid and/or gaseous media with an essentially parallelepiped-shaped base, means for feeding and removing the media (headers, supports), and a number of passages, arranged essentially like stacks, for indirect heat exchange between media that respectively flow into adjacent passages, whereby the passages are formed by partitions that are spaced some distance apart, whereby the partitions are spaced some distance apart by end strips, the passages have a corrugated profile (fins), which is in heat-conductive contact with the partitions at its wave peaks and wave troughs, and the stack is closed off by a cover plate. The invention is exemplified below as an oil or air cooler, but in principle, it can be used for any plate heat exchanger and therefore is not limited to the application that is described by way of example.

Plate heat exchangers are known in numerous embodiments and are laid out between at least two liquid and/or gaseous media for indirect heat exchange. The media that are involved in the heat exchange in this case flow through physically separated passages in the heat exchanger, so that the heat exchange is carried out only indirectly. The indirect heat exchange in this case is carried out via the structures, which separate the respective passages from one another, the thus mentioned partitions.

The partitions are arranged like stacks in a plate heat exchanger and are spaced some distance apart by end strips. The passages through which flow the media that are involved in each case in heat exchange are formed between the partitions. In general, the partitions have an essentially rectangular shape, so when arranged in a stack, an approximately parallelepiped plate heat exchanger is produced. According to the prior art, means for feeding and removing the respective media in the different passages are attached to the essentially parallelepiped structure.

According to the prior art, the passages have a corrugated profile, the thus mentioned fins. In the passages that are formed between the partitions, a corrugated profile is introduced, and said profile is in heat-conductive contact with the partitions at the respective reversal points of the corrugated structure, the wave peaks and wave troughs. In this case, the corrugated profile is perpendicular to the flow direction of the medium that flows through the passage. The heat exchange between two media that flow through adjacent passages is thus improved by the heat-conductive contact of the corrugated profile at the reversal points with the partitions.

In one application of such a plate heat exchanger according to the prior art as an oil or air cooler, the means for feeding and removing are designed in such a way that in each case oil flows alternately with air as a coolant through adjacent passages. If the coolers are used in compressors, the plate heat exchangers are often exposed to pressure and temperature changes. Such pressure or temperature changes are accompanied by high mechanical stresses and loads, which results in a high material requirement and quick material fatigue.

An object of this invention is therefore to provide plate heat exchangers of the above-mentioned type having an improved stability and fatigue strength.

Upon further study of the specification and appended claims, other objects and advantages of the invention will become apparent.

To achieve these objects, at least one new geometric ratio has been discovered which can lead to the improved fatigue strength and stability.

More specifically, a heretofore undisclosed result-effective variable provides that the ratio between the width of the partition and the repetition interval of the same characteristic of the corrugated profile as, for example, the repetition interval of two wave peaks (wavelength) or midpoints or minima has a value in the range of between 15 and 80. The ratio has not been addressed prior to the present invention.

Simulations of a plate heat exchanger, which is used as an oil cooler, show an improvement in the fatigue strength in the statistical mean by a factor of 10 in the embodiment according to the invention before fatigue rupture occurs.

Thus a concept of the invention is to increase stability by the suitable adaptation of the geometric parameters of the plate heat exchanger to one another. According to the invention, not merely parts of the plate heat exchanger can be designed more solidly to increase its stability, but rather the ratio between the wavelength and width of the partition is optimized. According to the invention, the division of how many corrugated structures (fins) are located on a partition of a given width is selected by setting the ratio of width of the partition to wavelength in such a way that the optimum stability and fatigue strength of the plate heat exchanger are achieved.

According to an advantageous configuration of the invention, the ratio between the width of the partition and the wavelength has a value in the range of between 20 and 60, preferably 28 and 50, and especially preferably 29 and 43.

Suitably, the ratio between the width and thickness of the partition is less than 150. In an advantageous configuration of the invention, the ratio between the width and thickness of the partition has a value in the range of between 50 and 150, preferably 75 and 115, and especially preferably between 80 and 105. By the additional optimization of partition width to partition thickness, another improvement in stability and fatigue strength is achieved.

Advantageously, the ratio of the height difference between the highest point of a wave peak and the lowest point of a wave trough (fin height) to the material thickness of the corrugated profile (fin thickness) is in the range of between 7 and 80 in passages through which oil flows as a medium. In one configuration of the invention, the ratio between fin height and fin thickness is in the range of between 8 and 20, preferably 10 and 15, in passages through which oil flows as a medium. Within the scope of the invention, it has proven advantageous to design the fins, in passages of the heat exchanger through which the hot oil that is to be cooled is conveyed, in such a way that the ratio between fin height and fin thickness is always between a value of 7 and 80.

It is also advantageous to design the end strip in such a way that the end strip has a bottom side and three blades that are perpendicular to it, whereby the three blades are oriented in such a way that they face the interior of the parallelepiped-shaped base, and the middle of the three blades is longer than the outer two blades. In this case, such an end strip according to the invention can have both several openings or recesses, through which the respective medium/media is/are conveyed into the passages. All intervals between two partitions on the two shorter sides of the partition are preferably closed off by such an end strip in each case. By the design with the three perpendicular blades on the bottom side, the mass of the end strip can be reduced, without in this case forfeiting mechanical stability. In an application as an oil cooler, the two longer sides are advantageously designed without end strips, and thus ambient air can flow through them as a coolant.

In an especially preferred configuration of the invention, the plate heat exchanger according to the invention is used as an oil or air cooler, whereby in particular hot oil is cooled in heat exchange with air. In such a use, the plate heat exchanger is exposed to especially high mechanical loads by the application-induced frequent fluctuation of temperature and/or pressure of the oil that is to be cooled. The high mechanical stability and fatigue strength achieved according to the invention are especially advantageously produced in such a use.

With this invention, it is possible to configure in particular a plate heat exchanger of the initially mentioned type in such a way that the mechanical stability and the fatigue strength of the plate heat exchanger, in particular with use under permanent fluctuation of the pressure and temperature conditions, can be considerably increased compared to the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein:

FIG. 1 shows a diagrammatic, perspective visualization of an embodiment of the plate heat exchanger according to the invention

FIG. 2 shows the same visualization as FIG. 1 without fittings

FIG. 3 a shows a diagrammatic, perspective visualization of a passage of the plate heat exchanger from FIGS. 1 and 2

FIG. 3 b shows a section from the cross-section of a passage according to FIG. 3 a

FIG. 4 shows a diagrammatic, perspective visualization of an exploded view of a second embodiment of the plate heat exchanger according to the invention

FIG. 5 shows the profile of end bar 4 a or 4 b.

DETAILED DESCRIPTION

FIG. 1 shows a plate heat exchanger from the outside. The plate heat exchanger has a central cuboid 8 with a length L of 1.1 m and a width B or height H of respectively 11 cm. On the top on the cuboid 8, on its sides and below the latter, mounted semicylindrical boxes 6 and 6 a (headers) are visible. Such mounted boxes are also located below the cuboid 8 and on the side that faces away from the side depicted. The latter are partially covered, however. By supports 7, fluids, here air and oil, can be fed to the plate heat exchanger or can be removed again from the latter. The headers 6 and 6 a are used for distribution of the media that are introduced by the supports 7 or for collecting and for concentrating the media that are to be removed from the plate heat exchanger and have a (wall) thickness of 8 mm (header 6) or 6 mm (header 6 a).

The plate heat exchanger that is shown in FIG. 1 is designed for more than two fluid streams to bypass one another in separate passages for heat exchange. A portion of the streams can be directed past one another in opposite directions, while another portion can be directed crosswise. To explain the invention, the simple situation is considered where an air stream and an oil stream flow crosswise to one another in separate, alternating passages. Larger numbers of fluid streams do not bring up any additional qualitative aspects within the scope of the invention.

In FIG. 2, it can be seen how the plate heat exchanger from FIG. 1 is built up in the interior. Essentially, the cuboid 8 is built from partitions 1 and corrugated profiles 2 (fins) or distributor profiles 3. Layers that have partitions 1 and profiles 2 or 3 alternate. An intermediate space between partitions 1, which is designed for a fluid to flow through it and which has profiles 2 and 3 here, is named passage 14 (such a passage is shown in FIGS. 3 a and 3 b and is described below.)

The cuboid 8 has alternating passages 14 and partitions 1 that are parallel to the directions of flow. Both the partition and the passages 14, i.e., the profiles 2 and 3, are made from aluminum. The partitions 1 have a thickness of 1.1 mm. On their sides, the passages 14 are closed off by aluminum end beams 4 a, so that a side wall is formed by the stack design with the partitions 1. The end beams 4 a have a width of 10 mm along the partition 1. The stacked partitions 1 of the cuboid 8 are closed off by aluminum cover plates 5 with a thickness of 6 mm that are parallel to the partitions 1. At their fronts, the passages 14 are closed off by aluminum end strips 4 b with a thickness of 5.5 mm along the partition.

The cuboid 8 has been produced by applying solder on the surfaces of the partition 1 and then alternately stacking the partitions 1 and the passages 14 one on top of the other. The cover plates 5 cover the stack 8 upward or downward. Then, the stack 8 has been soldered by heating in a furnace that comprises the stack 8.

On the sides of the plate heat exchanger, the distributor profiles 3 have distributor profile accesses 9 (cf. also FIG. 2, recesses in the end beams 4 a and end strips 4 b). By the latter, the fluids can be introduced from outside or also removed again in the related passages 14 via the headers 6 and 6 a and supports 7. The distributor profile accesses 9 that are shown in FIG. 2 are covered in FIG. 1 by the headers 6 and 6 a.

FIG. 3 a shows one of the passages 14 of the plate heat exchanger that is shown in FIGS. 1 and 2. The flow direction of the fluid is identified by arrows. The fluid flows in on one distributor profile access 9 to be distributed in the related distributor profile 3 to the entire width of the passage 14. Then, the fluid flows through the corrugated heat exchange profile 2 and is concentrated on the outlet-side distributor profile access 9 after the heat exchange from the other distributor profile 3 is completed. On their lateral sides and fronts, the passage 14 is limited by the end beams 4 a and the end strips 4 b.

FIG. 3 b shows a cutaway from a cross-section through the corrugated heat exchange profile 2 in FIG. 3 a. The profile 2 has a height HP of 4 mm and a profile thickness SP of 0.8 mm. The corrugated plot of the profile 2 is repeated within a wavelength LP of 1.6 mm. The ratio of partition width B to wavelength LP according to the invention is thus 69.

In FIG. 4, four passages of an air-oil-plate heat exchanger is shown in an exploded view without fittings.

A cuboid 30 that consists of partitions 22 and profiles 23 or 25 is closed off upward by a cover plate 21. Regarding the dimensions of the cuboid 30 and the cover plate 21 and partition 22 or for their materials, what is stated in FIGS. 1 and 2 applies here accordingly. The upmost-lying passage 27 is designed for air flowing through it; the passage 28 that is found thereunder is designed for oil flowing through it. Again, a passage that is designed for air, etc., flowing through it follows thereunder. In this plate heat exchanger, the air is conveyed crosswise to the longitudinal direction, and the oil along the longitudinal direction of the cuboid 30. The end strips 24 of the air-carrying passages 27 have a profile in the shape of a large “E,” whereby the dovetails of the large “E” point into the interior of the plate heat exchanger. These front end strips 24 have a thickness of 5.5 mm along the partition 22. The oil-carrying passages 28 are closed off by lateral end beams 26, which have a width of 12 mm along the partition 22. The profiles 23 in the air-carrying passages 27 are designed differently than the profiles 25 in the oil-carrying passages 28. In the air-carrying passages 27, the profiles 23 have a height of 6 mm, the structures are repeated with a wavelength of 3.5 mm, and the profile has a thickness of 0.8 mm. In the oil-carrying passages 28, the profile height is 3.5 mm, and the structures are repeated with a wavelength of 1.5 mm. The profile thickness is also 0.8 mm in the oil-carrying passages 28. In another configuration of the invention, the profile height is 5 mm with a profile thickness of 0.5 mm in the oil-carrying passages.

In FIG. 5, the profile of the end bar is shown along line AA. In FIG. 3 a, the opening of the E-type profile is directed to the fins of the passage 2 and therefore to the inner part of the heat exchanger. Above and below the E-type lamella would be a parting sheet. The middle lamella is a little longer than the other ones.

The plate heat exchangers that are described based on the preceding drawings are operated such that the fluid pressure and the temperature in the plate heat exchangers do not exceed 80 bar and 70° C. Also, in these plate heat exchangers, the fluid is fed so that pressure fluctuations remain below 50% of the design pressure, and the volume flow is 10 l/m inute in each passage during the heat exchange. Even if no heat exchange is carried out between oil and air, oil with a reduced volume flow of 0.5 l/minute also flows through the plate heat exchanger. This happens so that the plate heat exchanger remains at an elevated temperature. For a third embodiment (not shown), the properties of the plate heat exchanger from FIGS. 1 and 2 are adopted to a large extent. Unlike the first embodiment, only the lowermost two partitions and the uppermost two partitions have a thickness of 1.1 mm. The inside partitions have only a thickness of 0.8 mm. In addition, only the uppermost and the lowermost profiles have the values indicated in FIG. 3 b. Profiles in the interior have a greater height, a smaller profile thickness and a greater wavelength of the profile structure. In this configuration of the invention, the profile height 5 is 5 mm with a profile thickness of 0.5 mm in the oil-carrying passages. In this configuration, the wavelength LP is 2.5 mm with a partition width B of 11 cm.

To facilitate an understanding of the figures, the following list will be helpful:

REFERENCE SYMBOL LIST

-   1 Partition -   2 Heat Exchange Profile -   3 Distributor Profile -   4 a End Beam -   4 b End Strip -   5 Cover Plate -   6, 6 a Boxes -   7 Support -   8 Cuboid -   9 Distributor Profile Access -   14 Passage -   21 Cover Plate -   22 Partition -   23, 25 Profiles -   24 End Strip -   26 End Beam -   27 Air-Carrying Passage -   28 Oil-Carrying Passage -   30 Cuboid -   SP Profile Thickness -   LP Wavelength -   HP Passage Height -   B Cuboid Width -   H Cuboid Height -   L Cuboid Length

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

The entire disclosures of all applications, patents and publications, cited herein and of corresponding German application No. 10200803302.6, filed Jul. 15, 2008 are incorporated by reference herein.

The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. 

1. In a plate heat exchanger for indirect heat exchange between at least two liquid and/or gaseous media with an essentially parallelepiped-shaped base (8), means for feeding and removing the media (headers 6, 6 a, 7), and a number of passages (14), arranged essentially like stacks, for indirect heat exchange between media that respectively flow into adjacent passages (14), whereby the passages are formed by partitions (1, 22) that are spaced some distance apart, whereby the partitions are spaced some distance apart by end strips (4 a, 4 b), the passages have a corrugated profile (fins, 2), which is in heat-conductive contact with the partitions (1, 22) at its wave peaks and wave troughs, and the stack is closed off by a cover plate (5, 21), the improvement wherein the ratio between the width of the partition (B) and the repetition interval of the same characteristic of the corrugated profile (2) as, for example, the repetition interval of two wave peaks (wavelength, LP) has a value in the range of between 15 and
 80. 2. A plate heat exchanger according to claim 1, wherein the ratio between the width of the partition (B) and wavelength (LP) has a value in the range of between 20 and
 60. 3. A plate heat exchanger according to claim 1, wherein the ratio between the width (B) and the thickness of the partition is less than
 150. 4. A plate heat exchanger according to claim 3, wherein the ratio between the width (B) and the thickness of the partition has a value in the range of between 50 and
 150. 5. A plate heat exchanger according to claim 1, wherein the ratio of height difference (HP) between the highest point of a wave peak and the lowest point of a wave trough (fin height) to the material thickness (fin thickness, SP) of the corrugated profile (2), in passages (14) through which oil may flow as a medium, has a value in the range of between 7 and
 80. 6. A plate heat exchanger according to claim 1, wherein the ratio between fin height (HP) and fin thickness (SP), in passages (14) through which oil flows as a medium, has a value in the range of between 8 and
 20. 7. A plate heat exchanger for indirect heat exchange between at least two liquid and/or gaseous media with an essentially parallelepiped-shaped base (8), means for feeding and removing the media (headers 6, 6 a, 7), and a number of passages (14), arranged essentially like stacks, for indirect heat exchange between media that respectively flow into adjacent passages, whereby the passages (14) are formed by partitions (1, 22) that are spaced some distance apart, whereby the partitions (1, 22) are spaced some distance apart by end strips (4 a, 4 b), and the stack is closed off by a cover plate (5, 21), wherein the end strip (4 a, 4 b) has a bottom side and three blades that are perpendicular to it, whereby the three blades are oriented in such a way that they face the interior of the parallelepiped-shaped base, and the middle of the three blades is longer than the outer two blades.
 8. A method of cooling oil or air, comprising providing a heat exchanger according to claim 1 and passing oil or air there through in indirect heat exchange with a heat exchange medium.
 9. A plate heat exchanger according to claim 2, wherein said ratio is between 28 and
 50. 10. A plate heat exchanger according to claim 2, wherein said ratio is between 29 and
 43. 11. A plate heat exchanger according to claim 4, wherein said ratio is between 75 and
 115. 12. A plate heat exchanger according to claim 4, wherein said ratio is between 80 and
 105. 13. A plate heat exchanger according to claim 6, wherein said range is between 10 and
 15. 14. A plate heat exchanger according to claim 1, wherein the ratio of the height difference between the highest point of a wave peak and the lowest point of a wave trough (fin height) to the material thickness of the corrugated profile (fin thickness) is in the range of between 7 and 80 in passages through which oil flows as a medium.
 15. A plate heat exchanger according to claim 14, wherein, the ratio between fin height and fin thickness is in the range of between 8 and 20, through which oil flows as a medium.
 16. A plate heat exchanger according to claim 14, wherein, the ratio between fin height and fin thickness is in the range of between 10 and 15, in passages through which oil flows as a medium. 